Which Word Best Defines Casper: City or Town?

Whilst doing some daily internet research, I came across a myriad of national stories on different Wyoming locations. Jackson Hole, Cheyenne, Casper and Gillette were the most popular metropolitan locations. There was one major discrepancy within each story though and that was how to label these places. It got me to thinking, what constitutes a city and how does that differ from a town?

After a quick Google search, I was lead towards a term I had never heard before called: Settlement hierarchy. Wikipedia defines it as:

a way of arranging settlements into a hierarchy based upon their population or some other criteria.

For the most part, settlement hierarchy is used by England, but other countries such as Ireland, India and Switzerland also use it. By their standards, no populated area in Wyoming could be classified as a city. The main criteria to be considered a city is a population between 100,000 and 300,000.

To put this in perspective, the entire state population is estimated at just under 580,000. Here's a look at the most populated areas:

Cheyenne - 63,624

Casper - 57,815

Laramie - 32,306

Gillette - 30,560

Rock Springs - 23,350

Sheridan - 17,860

Jackson - 10,532

Going back to the Settlement hierarchy, that would mean Casper is a large town. Large towns are classified as having a population between 20,000 to 100,000.

One of the reasons this system isn't widely used worldwide (according to Wikipedia) is because:

using the size of a settlement can be misleading in some cases, as not all population boundaries are the same. In addition there is no agreement as to the number of levels in the hierarchy or what they should be called. Also many terms used to describe settlements (i.e. village) have no legal definition, or may have contradictory legal definitions in different jurisdictions.